WASHINGTON -- Lithium-ion batteries like the ones that overheated on two Boeing Co. 787 Dreamliners are "potent" but come with risks, the head of a federal safety board said during a forum Thursday."We know lithium-ion battery technology is an established technology -- its commercial use dates to 1991," Deborah A.P. Hersman, chairman of the National Transportation Safety Board, said during a forum on the batteries. "At the same time, it is an emerging technology with extensive and growing application in transportation."The NTSB convened the forum, which continues Friday, as part of an agency investigation of the Jan. 7 fire of a Boeing 787 in Boston. Boeing has proposed a redesigned battery system to the Federal Aviation Administration, which grounded the Dreamliner on Jan. 16.The NTSB will hold a separate hearing April 23-24 to examine the Dreamliner's battery design and how it was certified by the FAA."The batteries are continuing to get better and safer," Dan Doughty of Battery Safety Consulting in Albuquerque, N.M., said in an interview. "As we learn and understand the failure modes, that will continue."The question is whether safeguards such as encasing batteries in steel and building in protective circuitry are too costly, Vince Visco, senior vice president of strategy and business development at Quallion, said in an interview. Los Angeles-based Quallion makes batteries for use in space and medical devices. He and Doughty spoke Thursday at the NTSB forum in Washington.Part of Boeing's proposal includes increased spacing between lithium-ion battery cells. The move should decrease the likelihood that a fire in one cell could spread to others."One of the worries in the industry is if you have a cell failure, will it propagate?" Doughty said on Thursday. "If you can't prevent or predict a cell failure, it's essential to prevent propagation."In originally designing and testing the 787's battery, Boeing had believed a failure in one cell wouldn't spread to the next. But that wasn't the case in the Jan. 7 incident, according to NTSB findings. The NTSB has yet to determine the cause of the failure.Rechargeable lithium cells power devices ranging from Apple's iPad to power tools and are increasingly used in transportation. While battery fires are rare, they have been linked to aviation accidents and blazes in plug-in electric cars.When it catches fire, lithium burns violently, spewing flammable gas and molten metal. However, batteries much larger than those on the 787 have proven themselves in recent years in uses that include hybrid buses and power grids, Yet-Ming Chiang, a Massachusetts Institute of Technology professor who also spoke at the forum, said in an interview."Any time you have a highly concentrated source of energy, you need to understand it and treat it with respect," Chiang said. "But that's true of any form of fuel that you use, whether it's gasoline, jet fuel or batteries."The FAA has recorded 33 cases of batteries brought aboard commercial planes by passengers or as cargo catching fire since 2009. Of those cases, 26, or 79 percent, involved lithium-based batteries, according to the agency.Since 2006, three cargo jets have been destroyed in fires in which lithium batteries were present, according to the safety board. Those cells were being shipped and weren't part of the aircraft. The United Nations' International Civil Aviation Organization on Jan. 1 imposed new rules on air shipments of lithium batteries.Boeing got U.S. regulatory permission to install lithium-ion batteries on the Dreamliner in 2007, three years after passenger airlines were barred from carrying non-rechargeable battery types as cargo.Boeing chose them for the 787, which uses more electricity than previous designs, because they are lighter, hold more energy and can be quickly recharged, Mike Sinnett, the 787 chief project engineer, said in a January briefing.The greatest risk for lithium-ion batteries is that of overcharging, Bowling said. Companies like Boeing need to know how the battery they're using could fail and make sure the system the battery is used in will accommodate such failure.The FAA has not said how soon it will give Boeing an answer on the redesign. However, Boeing customers, like Qatar Airways, are speculating the 787 could be back in the air by the end of April.

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